What if a vacancy arises after the convention but before election day?
Here again the political parties would play a central role.
The Democratic National Committee and the Republican National Committee have slightly different rules guiding how they would replace the deceased presidential nominee by majority vote.
According to party rules, the DNC has the power to fill the vacancy on their party ticket after the chair consults Democratic governors and congressional leaders. The RNC, according to its rules, could reconvene a national convention or select the alternative candidate itself.
For simplicity, the parties would probably consider the running mate, but there is no guarantee.
If there were enough time, the replacement candidate might appear on the ballot. But states have different ballot filing deadlines and several states begin mailing their ballots as early as September.
In states where ballots have already been printed or mailed, the party could instruct voters – and electors – to treat the names at the top of the ticket “as hieroglyphics”, said Derek Muller, a law professor at the University of Notre Dame.
“If it says Biden-Harris, you should interpret that as Harris-Booker,” he said, offering the hypothetical example of an alternative Democratic ticket with the New Jersey senator Cory Booker as Harris’s running mate.
https://www.theguardian.com/us-news/...ump-biden-dies